// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GFX_CODEC_PNG_CODEC_H_
#define UI_GFX_CODEC_PNG_CODEC_H_

#include <stddef.h>

#include <string>
#include <vector>

#include "base/macros.h"
#include "ui/gfx/gfx_export.h"

class SkBitmap;

namespace gfx {

class Size;

// Interface for encoding and decoding PNG data. This is a wrapper around
// libpng, which has an inconvenient interface for callers. This is currently
// designed for use in tests only (where we control the files), so the handling
// isn't as robust as would be required for a browser (see Decode() for more).
// WebKit has its own more complicated PNG decoder which handles, among other
// things, partially downloaded data.
class GFX_EXPORT PNGCodec {
public:
    enum ColorFormat {
        // 3 bytes per pixel (packed), in RGB order regardless of endianness.
        // This is the native JPEG format.
        FORMAT_RGB,

        // 4 bytes per pixel, in RGBA order in memory regardless of endianness.
        FORMAT_RGBA,

        // 4 bytes per pixel, in BGRA order in memory regardless of endianness.
        // This is the default Windows DIB order.
        FORMAT_BGRA,

        // SkBitmap format. For Encode() kARGB_8888_Config (4 bytes per pixel) and
        // kA8_Config (1 byte per pixel) formats are supported. kA8_Config gets
        // encoded into a grayscale PNG treating alpha as the color intensity.
        // For Decode() kARGB_8888_Config is always used.
        FORMAT_SkBitmap
    };

    // Represents a comment in the tEXt ancillary chunk of the png.
    struct GFX_EXPORT Comment {
        Comment(const std::string& k, const std::string& t);
        ~Comment();

        std::string key;
        std::string text;
    };

    // Encodes the given raw 'input' data, with each pixel being represented as
    // given in 'format'. The encoded PNG data will be written into the supplied
    // vector and true will be returned on success. On failure (false), the
    // contents of the output buffer are undefined.
    //
    // When writing alpha values, the input colors are assumed to be post
    // multiplied.
    //
    // size: dimensions of the image
    // row_byte_width: the width in bytes of each row. This may be greater than
    //   w * bytes_per_pixel if there is extra padding at the end of each row
    //   (often, each row is padded to the next machine word).
    // discard_transparency: when true, and when the input data format includes
    //   alpha values, these alpha values will be discarded and only RGB will be
    //   written to the resulting file. Otherwise, alpha values in the input
    //   will be preserved.
    // comments: comments to be written in the png's metadata.
    static bool Encode(const unsigned char* input,
        ColorFormat format,
        const Size& size,
        int row_byte_width,
        bool discard_transparency,
        const std::vector<Comment>& comments,
        std::vector<unsigned char>* output);

    // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
    // to be kARGB_8888_Config, 32 bits per pixel. The params
    // |discard_transparency| and |output| are passed directly to Encode; refer to
    // Encode for more information. During the call, an SkAutoLockPixels lock
    // is held on |input|.
    static bool EncodeBGRASkBitmap(const SkBitmap& input,
        bool discard_transparency,
        std::vector<unsigned char>* output);

    // Call PNGCodec::Encode on the supplied SkBitmap |input|. The difference
    // between this and the previous method is that this restricts compression to
    // zlib q1, which is just rle encoding.
    static bool FastEncodeBGRASkBitmap(const SkBitmap& input,
        bool discard_transparency,
        std::vector<unsigned char>* output);

    // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
    // to be kA8_Config, 8 bits per pixel. The bitmap is encoded as a grayscale
    // PNG with alpha used for color intensity. The |output| param is passed
    // directly to Encode; refer to Encode for more information. During the call,
    // an SkAutoLockPixels lock is held on |input|.
    static bool EncodeA8SkBitmap(const SkBitmap& input,
        std::vector<unsigned char>* output);

    // Decodes the PNG data contained in input of length input_size. The
    // decoded data will be placed in *output with the dimensions in *w and *h
    // on success (returns true). This data will be written in the 'format'
    // format. On failure, the values of these output variables are undefined.
    //
    // This function may not support all PNG types, and it hasn't been tested
    // with a large number of images, so assume a new format may not work. It's
    // really designed to be able to read in something written by Encode() above.
    static bool Decode(const unsigned char* input, size_t input_size,
        ColorFormat format, std::vector<unsigned char>* output,
        int* w, int* h);

    // Decodes the PNG data directly into the passed in SkBitmap. This is
    // significantly faster than the vector<unsigned char> version of Decode()
    // above when dealing with PNG files that are >500K, which a lot of theme
    // images are. (There are a lot of themes that have a NTP image of about ~1
    // megabyte, and those require a 7-10 megabyte side buffer.)
    //
    // Returns true if data is non-null and can be decoded as a png, false
    // otherwise.
    static bool Decode(const unsigned char* input, size_t input_size,
        SkBitmap* bitmap);

private:
    DISALLOW_COPY_AND_ASSIGN(PNGCodec);
};

} // namespace gfx

#endif // UI_GFX_CODEC_PNG_CODEC_H_
